Updated 6:39 p.m. | The race is on to succeed Rep. Henry A. Waxman as the top Democrat on the Energy and Commerce Committee, and it’s probably going to get personal.

Just four days after the 20-term California Democrat announced he would retire by the year’s end, fellow Californian Anna G. Eshoo and Frank Pallone Jr. of New Jersey officially threw their hats in the ring, with the dean of the House, John D. Dingell of Michigan, still considering a run of his own.

“I have received the encouragement of members of the Committee and the Caucus to seek this position,” Eshoo said in a statement on Monday. “I do so with great enthusiasm because ... [it] is key to shaping America’s future, just as my Silicon Valley congressional district is.”

“For over 20 years, I have remained deeply committed to advancing the goals of our great Committee,” Pallone said in a statement of his own. “As the person tasked with developing the Democratic Caucus’ message on the House Floor, I believe I would be the most effective voice to lead the Committee toward a successful future.”

Both lawmakers have certain advantages. Pallone is the committee’s No. 3 Democrat, and the House Democratic Caucus generally likes to reward members based on seniority. But Eshoo, the fifth-most-senior Democrat on the panel, has a trump card of her own: She is a close friend of Minority Leader Nancy Pelosi, D-Calif.

For the most part, however, their bona fides are so similar that lobbyists, political operatives and congressional aides predict that the battle for the ranking member slot will ultimately be about leveraging alliances rather than drawing distinctions on specific policy stances — that would be a tall order for two lawmakers with nearly identical voting records across the spectrum of issues in the committee’s portfolio.

In the words of a former longtime Democratic staffer on Capitol Hill, the race between Eshoo and Pallone is bound to become “a personal relationship contest.”

“If it’s only between Pallone and Eshoo, then it comes down to ... who do members like better? Who has shown up in their district to raise money for them? Who has gotten an amendment into a bill for them?” said a lobbyist who deals with issues that regularly come before the Energy and Commerce Committee.

Both members have served on Capitol Hill for more than two decades, so they have deep wells of support from which to draw. Pallone can seek out endorsements from members of the Congressional Progressive Caucus, to which he belongs, while Eshoo can exact votes from her state’s substantial Democratic delegation.

The fight could without a doubt get messy, as Eshoo and Pallone over the next 11 months fight to win over colleagues, many of whom likely consider each member to be a friend.

But the wild card in all this is Dingell.

The 87-year-old Michigan Democrat says he is going to consult with colleagues before making a decision. He served as both ranking member and chairman of the Energy and Commerce Committee for many years until 2008, when Waxman wrested the gavel from his hands.

Dingell could decide he wants his old job back, and his colleagues could be inclined to let him have it. Many long-serving Democrats felt sympathy for Dingell in the wake of his defeat and could want to reinstall him as a belated peace offering.

Other Democrats who supported Waxman’s challenge to Dingell in 2008 did so because they wanted a more progressive chairman to champion cap-and-trade legislation. With the party in the minority — now and in the foreseeable future — there’s less of a danger having Dingell representing the party on the panel, one health care lobbyist posited.

Plus, if Democrats are going to fall back on their deference to seniority, there’s no one more senior than Dingell.

It's also unclear if other lawmakers might get in the race. Rep. Bobby L. Rush of Illinois, the No. 4 Democrat on the panel, is on a leave of absence tending to his wife's health and that is his primary focus for now, a spokeswoman said.

Outside groups could also have an impact on the margins, although outside endorsements didn’t help Rep. Raúl M. Grijalva of Arizona last year when he launched an insurgent effort to edge out Rep. Peter A. DeFazio of Oregon for the top Democratic slot on the Natural Resources Committee.

It has, however, been known to happen, according to Dan Weiss, the director of climate strategy at the liberal-leaning Center for American Progress.

“After the Republicans won the House in 2010,” he said, “several members in line to become committee chairs made efforts to ensure that they were acceptable to the tea party and other very conservative organizations.”

There have also been cases where conventional wisdom fell on its head in terms of Democrats' deference to seniority, such as when Rep. Marcy Kaptur, D-Ohio, next in line to be ranking member of the Appropriations Committee, lost out to Rep. Nita M. Lowey, D-N.Y., in part because of the Ohioan's more conservative voting record. Indeed, Waxman wresting the gavel from Dingell had many wondering then if the seniority system was on its way out.

Generally speaking, however, every ranking member race is different, and searching for precedent might not be a good use of time, a House Democratic leadership aide cautioned.